Not really, although there have been people I've suspected of ping hacks of some sort, though really just in my frustration in being killed because of poor connections, caused probably by a jump in the number of players due to the stimulus package. But, in general, I've run into very few people I've suspected of hacking, and I've never heard anyone openly accuse someone of hacking.
Sounds good Well the problem with the PC community is that they'll accuse you on the spot for hacking if say... you're doing well with a sniper rifle doing some quick scoping etc... and it gets annoying as hell. Seeing from those guys perspective, if you're doing really well, the only explanation is hacking. And that's it. Obviously if they're doing good it's just skill...

I didn't see much on the first one...but I played it at my friends house, so I didn't experience it enough to tell. I saw some guy flying/clipping through everything once, but other than that, it didn't seem abundant.
ah yes... well flying/clipping is obviously easy to spot It gets more bizzare when players start accusing you of wall hacking / aimbotting even if there isn't any signs of it at all... or if you were just being lucky.